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Molecular technology for hospital epidemiology.

Hospital-acquired infections in the United States contribute to approximately 80,000 deaths per year, with an associated cost of > $4 billion. Some of these infections are associated with outbreaks and clusters occurring within the hospital. The hospital infection control team must respond quickly and decisively to recognize and curtail these outbreaks, but their response often depends on critical laboratory data that characterize or "fingerprint" suspected microbial isolates. This presentation summarizes the simple, easily performed tests and the more molecular approaches that a hospital laboratory may take in support of infection control efforts. In addition to phenotypic data, such as biotype and antibiograms, hospitals that elect to incorporate molecular protocols should limit their first experiences to plasmid analysis and plasmid restriction endonuclease profiles.

Cross Infection↗

Effective reporting of susceptibility test results.

An overview of effective reporting of susceptibility test results is presented. Areas included in effective antimicrobial reporting are selective reporting of antimicrobials within drug families and by specific drug-organism combinations, automatic computer-delivered susceptibilities to patient-care areas, "flagged" results that are unusual and/or could seriously effect patient care, and the use of a coherent report format. Also included are areas that may significantly enhance antimicrobial result formats such as the reporting of cost information with susceptibility results, reporting "predictive sensitivities" based on institutional antibiograms, and reporting specific drugs for therapy based on gram's stain, and preliminary and final culture information.

Anti-Bacterial Agents↗

Econotherapeutics.

A program that represents the efforts of a hospital pharmacy management company to control drug costs is described. The program, Econotherapeutics, was developed in response to a changed health care reimbursement system that focused on the costs of products rather than the revenue generated by these products. For antimicrobial agents, a hospital-specific antibiogram is used to encourage cost-effective prescribing. A pharmacist intervention program, medical staff presentations, drug usage evaluation, management systems, and educational programs for pharmacists are all essential parts of the program. Centralized data gathering has allowed cost comparison of specific antimicrobial agents so that differences between variable cost estimates and costs based on actual use can be evaluated. Actual dose and dosage interval were used to calculate average cost per treatment day in a 121-hospital sample. Our cost data support the choice of cefotaxime over ceftriaxone.

Anti-Bacterial Agents↗

Survey of antimicrobial activity of four commonly used third generation cephalosporins tested against recent bacterial isolates from ten American medical centers, and assessment of disk diffusion test performance. AST Surveillance Group.

Over 2,000 clinical isolates from ten American medical centers were tested for susceptibility to cefotaxine, ceftriaxone, ceftizoxime, and ceftazidime by both broth microdilution and disk diffusion methods. Typically resistant (e.g. enterococci) and highly susceptible (e.g. streptococci) isolates showed no change in susceptibility patterns compared to previous surveys. Pseudomonas aeruginosa and Stenotrophomonas maltophilia exhibited significant decreases in susceptibility to these cephalosporins. Among Escherichia coli and Klebsiella spp isolates, two to three percent were resistant to one of the four drugs whereas they were very susceptible to the other three. Of the four antibiotics, the cefotaxime disk diffusion test results correlated best with the microdilution results. With the other three drugs the disk diffusion test yielded 1 to 9% more susceptible test results and 1 to 20% fewer resistant test results than broth microdilution when testing gram negative bacilli. The clinical significance of such discrepancies is not known, but the impact on antibiotic susceptibility surveys and antibiogram comparisons could be significant.

Ceftazidime↗

Antibiotic treatment of Lyme borreliosis.

Unlike most bacterial infections, where diagnosis is by identification of the causal organism, diagnosis of infection by Borrelia burgdorferi (Lyme's borreliosis) relies mostly upon indirect techniques. This situation has some short-comings. As long as no technology permits a microbiological diagnosis of this infection, controversy will exist as to the clinical symptoms and the criteria for the cure of the disease. Despite the lack of consensus upon both the clinical definition and the treatment of Lyme's borreliosis, it is widely agreed that the affection is best understood if regarded as a progressive general infectious disease. Indeed, following a bite with local infection, there occurs a fairly rapid dissemination of the spirochaetes. In vivo therapeutic trials have shown the potential effectiveness of beta-lactams and tetracyclines, but no treatment is considered universally effective. Most of the first trials were empirical, as antibiograms were not used. Antibiotic concentrations reached with some oral therapies are too low for the protection of certain sites such as the central nervous system. In vitro studies conducted on various strains of B. burgdorferi both in the US and in Europe are very enlightening. Among the more perplexing results of some of these studies, it is worth noting the high resistance rate of some B. burgdorferi strains to penicillin, reported by Johnson et al. and by Preac Mursic et al. Therapy for Lyme's borreliosis is discussed in light of both the in vivo and in vitro studies.

Borrelia↗

[Pneumococcal meningitis in children: should probabilistic antibiotherapy of infectious meningitis be modified?].

BACKGROUND: Since a significant proportion of Streptococcus pneumoniae strains is now resistant to penicillin and sometimes to third-generation cephalosporin, it is necessary to reevaluate the initial therapy of bacterial meningitis proposed before identification of the organism and its susceptibility pattern. POPULATION: From 1 January 1992 to 31 March 1994, nine children with acute S pneumoniae meningitis were treated with ceftriaxone plus aminoglycoside as conventional initial therapy. Eight children were less than 1 year-old (five from 3 to 6 months). Five S pneumoniae strains were penicillin-resistant; four had a ceftriaxone minimal inhibitory concentration (MIC) of 0.047 to 0.094 mg/L and one of 1.5 mg/L. Ceftriaxone was given intravenously at doses of 50 mg/kg twice a day to patients less than 12 months old and 100 mg/kg once a day to patients older than 12 months. Intravenous amikacin (7.5 mg/kg twice daily) or netilmicin (3 mg/kg twice daily) were administered in combination. Dexomethasone was given to all children as adjunctive therapy. Follow-up lumbar puncture was performed after 24 to 36 hours of treatment. RESULTS: For each of the nine patients, cerebrospinal fluid was sterile with normal glucose level. After 2 or 4 days, initial therapy had been modified according to antibiogram and MIC. Monotherapy with ceftriaxone was continued in five children. Rifampicin was associated with initial bitherapy in one case. In two other patients, initial empiric therapy was stopped and changed to chloramphenicol. CONCLUSION: No case of bacteriological failure was noted in our patients but evolution of epidemiology and emergence of decreased penicillin sensibility in S pneumoniae strains (55% in our study) suggests that a third antibiotic (vancocin or rifampicin) should be associated with the standard first-line drug when S pneumoniae is suspected.

Adolescent↗

Enteric gram-negative bacilli bloodstream infections: 17 years' experience in a neonatal intensive care unit.

OBJECTIVE: To assess the occurrence of enteric gram-negative bacilli (EGNB) bloodstream infections (BSI) in a neonatal intensive care setting during a 17-year period in which a consistent antibiotic treatment program was in place. To document infections, outbreaks, or epidemics, emergence of antibiotic resistance, clinical correlates, and outcomes of the most prevalent EGNB (Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae). METHODS: This study analyzed demographic, clinical, and bacteriologic information from 360 infants born 1986-2002 who developed 633 blood culture-proven BSI. A total of 121 EGNB were isolated (E coli, K pneumoniae, and E cloacae). Early-onset BSI were discovered within 48 hours from birth, and late-onset BSI were those that occurred thereafter. Suspected early-onset BSI were treated with ampicillin and gentamicin, suspected late-onset BSI with vancomycin and gentamicin. Antibiotics were changed on the basis of organism antimicrobial susceptibility. RESULTS: Early-onset BSI were noted in 52 of 21,336 (244/100,000) live births (1986-1991), 40 of 20,402 (196/100,000) live births (1992-1997), and 25 of 17,926 (139/100,000) live births (1998-2002). Of these cases, 39 were caused by E coli and 4 by K pneumoniae. Antibiograms for E coli isolated during the last 5 years of the study showed an increase in antibiotic resistance that coincided with obstetric group B streptococcus antepartum antibiotic prophylaxis. Group B streptococcus declined from 41 to 4 cases from the first to the last period. Late-onset BSI increased from 111 to 230 cases from the first to the second 6-year study period and declined modestly (171 cases) during the last. Fifteen percent (78 cases) of late-onset BSI were caused by EGNB, 5% by other gram-negative bacilli, 67% primarily by coagulase-negative staphylococcus, and 13% by fungus. Nonspecific clinical and hematologic signs of late-onset BSI were similar across EGNB species, but necrotizing enterocolitis was often associated with E coli, whereas pneumonia and prolonged thrombocytopenia characterized K pneumoniae infections. No outbreaks or epidemics were observed, and strains of EGNB with evidence of extended spectrum beta-lactamase production were never isolated. CONCLUSION: Antepartum antibiotic prophylaxis may have increased antibiotic resistance in E coli isolates from early-onset BSI but has dramatically decreased group B streptococcus infections. Late-onset BSI caused by EGNB increased, but without changes in antibiotic susceptibility. In spite of medical advances, E coli, K pneumoniae, and E cloacae remain responsible for significant morbidity and mortality, especially in very low birth weight infants.

Analysis of Variance↗

[Monitoring of antibiotic treatment of patient with a severe bacterial infection].

OBJECTIVES: To provide a summary of useful up-to-date knowledge regarding experimental and clinical bacteriology, pharmacokinetics and pharmacodynamics in order to optimise efficacy of antibiotic treatment of hospital patients with serious bacterial infections. DATA SOURCES: Record of references from national and international journals in Medline. STUDY SELECTION: Extraction of the most relevant theoretical and practical data from studies published over the last 5 years. DATA SYNTHESIS: Changes in resistance to antibiotics, as well as the limited number of new antibacterial drugs available and the cost of therapeutic failure all militate in favour of a more elaborate approach to therapeutic strategies involving antibiotics, particularly regarding hospitalised patients. The efficacy of antibiotic therapy can be optimised through the utilization of bacteriological, pharmacokinetic and pharmacodynamic data, thereby increasing the likelihood of a successful outcome. While the antibiogram constitutes the fundamental analytical tool for evaluating the activity of antibiotics, the minimum inhibitory concentration (MIC) is of value in selecting appropriate drugs and dosages, particularly for bacterial strains having lower susceptibility. Screening for genes of resistance to antibiotics provides more accurate analysis of bacterial resistance. In recent years, the efficacy of antibiotics has been improved through the use of a number of pharmacodynamic parameters: inhibitory quotient (IQ), area under the serum concentration-time curve to MIC ratio (AUC/MIC) and the time the serum concentration is greater than the MIC (T > MIC). In standard practice, data readily available to the clinician comprise the MIC and serum antibiotic concentrations. There is some discussion concerning optimisation of antibiotic efficacy through the use of these parameters. CONCLUSION: Close collaboration between clinicians and microbiologists results in improved quality of antibiotic therapy and better management of antibiotics.

Anti-Bacterial Agents↗

The time-related changes of antimicrobial resistance patterns and predominant bacterial profiles of burn wounds and body flora of burned patients.

To examine the bacterial isolates from the burn patients and to compare the antibiograms of the predominant bacteria isolated from 51 patients who were hospitalized at least 3 weeks or more over a period of 7 months, a prospective study was undertaken. Periodic swabs were taken from burn wound, nasal, axillary, inguinal, and umbilical region of the patients on admission and on 7th, 14th, and 21st days of hospitalization. Mean hospital stay was 36.5 days. A total of 1098 microbial isolates were detected during the study period. Coagulase-negative staphylococci (CNS, 63.0%) and Staphylococcus aureus (19.7%) were the most prevalent isolates in admission cultures. During the next weeks, these bacteria were superceded by mainly Pseudomonas aeruginosa. Between admission and 21st day, the rates of methicillin resistance of staphylococci strains increased steadily. There was no vancomycin resistance in any staphylococci strains, although nine of the S. aureus isolates (2.7%) were resistant to teicoplanin. There were no strains producing inducible beta lactamase (IBL) among P. aeruginosa strains. One extended-spectrum beta-lactamase (ESBL)-producing strain was recovered on admission, although strains producing IBL and ESBL were detected at rates of 79.6 and 57.1%, respectively, on the 21st day. The nature of microbial wound colonization, flora changes, and antimicrobial sensitivity profiles should be taken into consideration in using empirical antimicrobial therapy of burned patients.

Adolescent↗

Antibiotic-resistant infections in the critically ill adult.

Intensive care units (ICUs) frequently are the epicenter of nosocomial infections with antibiotic-resistant bacteria. Optimization of antibiotic therapy for seriously ill patients with bacterial infections appears to have a strong influence on outcome. Laboratories can aid in provision of appropriate antibiotic therapy by providing clinicians with "antibiograms" to aid empiric antibiotic choice and by providing minimal inhibitory concentrations of key antibiotics so that antibiotic dosing is optimized to key pharmacodynamic targets. Laboratories also play a crucial role in the prevention of antibiotic resistance in the ICU. Molecular epidemiologic evidence of an oligoclonal outbreak of infections orients prevention measures toward investigation of common environmental sources of infection and prevention of patient-to-patient transmission. In contrast, evidence of polyclonality shifts prevention of antibiotic resistance to antibiotic management strategies.

Adult↗

The role of antifungal susceptibility testing in the therapy of candidiasis.

Prior to the introduction of azoles, no real need for antifungal susceptibility testing (AFST) existed, as amphotericin B was the only agent available to treat systemic candidiasis. Introduction of fluconazole and itraconazole provided alternate, less toxic antifungal therapies. Intrinsic resistance of Candida krusei, decreased susceptibility of Candida glabrata, and development of resistance by Candida albicans (in mucosal disease in AIDS) to azoles led to development of our current AFST methodologies. The goal of AFST, like that of antibacterial susceptibility testing, is to predict clinical response, or at least to forecast failure. Although the ability of AFST to predict clinical outcome (clinical correlation) is still being fully elucidated, current methodologies do appear to reliably predict clinical resistance to azoles. Ready access to AFST is currently limited, affecting its timely use, but even with this lack of timeliness, AFST can still play an important role in patient care. Important potential roles include: 1) use in the development of local antibiograms to aid empiric selection of antifungals; 2) testing of isolates from candidemia or deep infection to aid in selection of long-term therapies; and, 3) the testing of isolates from recurrent mucosal disease to aid in selection of alternative regimens.

Antifungal Agents↗

Survey of CTX-M-3 extended-spectrum beta-lactamase (ESBL) among cefotaxime-resistant Serratia marcescens at a medical center in middle Taiwan.

Thirty-four clinical isolates of Serratia marcescens nonsusceptible to cefotaxime were collected from a medical center in middle Taiwan. Confirmatory tests for extended-spectrum beta-lactamases (ESBLs) by cefotaxime and ceftazidime +/- clavulanic acid using Etest ESBL Screen identified only one ESBL producer; the remaining 33 isolates revealed nondeterminable results, because of off-scale minimum inhibitory concentration (MIC) levels for cefotaxime +/- clavulanic acid. Agar microdilution method using broader MIC ranges confirmed 21 ESBL-producers and one non-determinable result, achieving a highly predicting value compared to golden standard by PCR and DNA sequencing analysis, which identified 22 (65%) isolates containing blaCTX-M-3 genes. Only one strain carried concurrent CTX-M-3 and SHV-5 conferring high-level MICs to both cefotaxime (128 microg/mL) and ceftazidime (64 microg/mL). Other enzymatic mechanisms, such as chromosome-encoded AmpC including a novel SRT-2 enzyme, may confer resistance to cefotaxime on the remaining 12 isolates without ESBL bla genes. Thus, it is unreliable to predict the resistance mechanism by antibiogram, and current Etest ESBL Screen tests. Our study highlights expanding efforts to detect ESBLs in S. marcescens are urgently needed in Taiwan.

Anti-Bacterial Agents↗

Pharmacodynamic comparisons of antimicrobials against nosocomial isolates of escherichia coli, klebsiella pneumoniae, acinetobacter baumannii and pseudomonas aeruginosa from the MYSTIC surveillance program: the OPTAMA Program, South America 2002.

The OPTAMA (Optimizing Pharmacodynamic Target Attainment using the MYSTIC [Meropenem Yearly Susceptibility Test Information Collection] Antibiogram) Program provides insight into the appropriate antibiotic options for empiric therapy for common nosocomial pathogens. In this report, South America is represented by Brazil, Colombia, Peru, and Venezuela. A 5000-subject Monte Carlo Simulation estimated pharmacodynamic target attainment for meropenem, imipenem, ceftazidime, cefepime, piperacillin/tazobactam, and ciprofloxacin against Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Pharmacokinetic parameter variability was derived from existing healthy volunteer data, and minimum inhibitory concentration (MIC) data came from the 2002 MYSTIC program. Piperacillin/tazobactam and ciprofloxacin displayed the lowest target attainment against all bacterial species (14% to 24% for A. baumannii, 26% to 37% for P. aeruginosa, and 48% to 66% for the Enterobacteriaceae). Overall, the carbapenems had the highest probabilities of attainment against the Enterobacteriaceae (98% to 100%) and A. baumannii (73% to 74%), whereas cefepime obtained the greatest target attainment against P. aeruginosa (65%). Because no single regimen had high target attainment against A. baumannii and P. aeruginosa, the use of combination therapy to treat these pathogens in South America may be justified. Because of the lack of agreement with percent susceptibility for certain antimicrobial regimens, the use of pharmacodynamic target attainment may be a more accurate predictor of microbiologic success.

Acinetobacter baumannii↗

Therapeutic options among broad-spectrum beta-lactams for infections caused by levofloxacin-nonsusceptible Streptococcus pneumoniae.

Streptococcus pneumoniae has consistently become more resistant to primary, orally administered treatment regimens used for community-acquired respiratory tract infections (CARTI; sinusitis, bronchitis, pneumonia). As resistance rates approach 40-50% in the United States and North America for penicillin and macrolides, other agents also have exhibited coresistance rates of 10-20% (tetracycline, clindamycin, trimethoprim/sulfamethoxazole). These facts led to altered clinical treatment guidelines (IDSA) supporting the use of respiratory fluoroquinolones (levofloxacin, gatifloxacin, gemifloxacin, and moxifloxacin). This report from the SENTRY Antimicrobial Surveillance Program lists possible parenterally administered treatment alternatives for the fluoroquinolone (levofloxacin)-nonsusceptible pneumococci. The SENTRY Program isolates from CARTI (1997-2003), totaling 21605 strains from Europe, Asia Pacific, and the Americas, were screened for fluoroquinolone-resistant S. pneumoniae. A total of 157 (0.7%) levofloxacin-nonsusceptible (MIC > or = 4 microg/mL) strains were identified and tested by reference broth microdilution methods against 27 antimicrobials. Quinolone resistance-determining region (QRDR) mutations were determined by PCR amplification and gene sequencing. The entire population of S. pneumoniae had the following antibiogram demographics: penicillin-nonsusceptible (32%), macrolide resistance (24%), tetracycline resistance (21%), clindamycin resistance (11%), trimethoprim/sulfamethoxazole resistance (33%), and 6% of strains were resistant to all 5 drugs. Levofloxacin-resistant strains routinely had 2 or more QRDR mutations most frequently in gyrA at Ser81Phe or Tyr and in parC at Ser79Phe or Tyr and Lys137Asn. Four agents had extremely low rates of resistance when tested against the 157 levofloxacin-nonsusceptible strains (e.g., quinupristin/dalfopristin, 0% resistance; vancomycin, 0%; cefepime, 1%; ceftriaxone, 1%). Levofloxacin-nonsusceptible pneumococcal isolates remain uncommon, but are a growing problem in CARTI (1.4% in 2003), especially in previously fluoroquinolone-treated cases. Parenteral cephalosporins (cefepime or ceftriaxone) continue to be potent and safe for use in hospitalized patients with S. pneumoniae community-acquired pneumonia, used with or without co-drugs according to published guidelines.

Anti-Bacterial Agents↗

Tigecycline activity tested against 26,474 bloodstream infection isolates: a collection from 6 continents.

The activity of tigecycline (formerly GAR936), a novel glycylcycline, was tested against recent bloodstream infection (BSI) pathogen isolates from 6 continents. Frequency of clinical occurrence of these pathogens was determined and their antibiograms assessed using reference broth microdilution methods. A total of 26474 strains were tested for tigecycline susceptibility according to the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) by the M7-A6 guidelines with interpretations from M100-S15 and the package insert. The rank order of pathogens was Staphylococcus aureus (33.1%), Escherichia coli (14.0%), coagulase-negative staphylococci (13.5%), Enterococcus spp. (12.3%), Klebsiella spp. (5.7%), Pseudomonas aeruginosa (4.2%), Enterobacter spp. (3.0%), beta-hemolytic streptococci (2.9%), Streptococcus pneumoniae (2.3%), and viridans group streptococci (1.4%). Tigecycline exhibited a broader spectrum of activity against BSI isolates when compared to ciprofloxacin, tetracycline, aminoglycosides, and many beta-lactams (imipenem). Tigecycline was highly active against most pathogens tested, including staphylococci (MIC(90), 0.5 microg/mL), enterococci (MIC90, 0.25 microg/mL), streptococci (MIC(90), < or =0.12 microg/mL), Escherichia coli (MIC90, 0.25 microg/mL), Klebsiella spp. (MIC90, 1 mmicrog/mL), and Enterobacter spp. (MIC(90), 2 mmicrog/mL), but showed limited inhibition of Pseudomonas aeruginosa (MIC90, 16 microg/mL) and indole-positive or indole-negative Proteae (MIC90, 4-8 microg/mL). In summary, tigecycline exhibited a wide spectrum of antimicrobial potency versus BSI isolates collected worldwide. Serious infections in nosocomial environments should benefit from tigecycline use among the investigational phase 3 agents focused toward resistant strains.

Anti-Bacterial Agents↗

Imipenem-resistant Achromobacter xylosoxidans carrying blaVIM-2-containing class 1 integron.

We characterized seven isolates of imipenem-resistant Achromobacter xylosoxidans that were isolated from patients hospitalized in the intensive care unit at a tertiary hospital in Korea during 2001 to 2003. From the analysis with an isoelectric focusing, polymerase chain reaction, and sequencing methods, all isolates were found to produce VIM-2, OXA-30, and chromosomal AmpC beta-lactamase with a pI of 8.4. They showed a similar antibiogram, which were resistant to all tested aminoglycosides as well as beta-lactams including imipenem (16-32 mg/L) and aztreonam (128 mg/L), and a same DNA fingerprinting pattern by random amplified polymorphic DNA analysis, suggesting that these originated from a single clone. From the analysis of integron structure carried by an isolate of A. xylosoxidans CBU1760, bla(VIM-2) was found to be part of a gene cassette carried on a class 1 integron (3.4 kb) containing three aacA4 gene cassettes. This is the first report of bla(VIM-2) in A. xylosoxidans.

Achromobacter denitrificans↗

Making the most of surveillance studies: summary of the OPTAMA Program.

Antibiotic surveillance studies lack consideration of pharmacodynamics and provide little information about optimal dosing. By using minimum inhibitory concentration (MIC) data derived from a global surveillance study and Monte Carlo simulation, the Optimizing Pharmacodynamic Target Attainment using the MYSTIC Antibiogram (OPTAMA) Program was established to impart greater understanding of the ability to attain pharmacodynamic exposure for specific dosing regimens and their relationship with percent susceptibility. Early OPTAMA studies focused on determining the cumulative fraction of response (CFR) for various antibiotics against Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa regionally in Europe and the Americas. Later reports considered the prevalence of specific bacteria causing infections to estimate the CFR for empiric therapy of pneumonia, bloodstream, complicated skin/skin structure, and intra-abdominal infections. Collectively, the approach of the OPTAMA Program provides a novel tool that complements susceptibility data to help in the selection of appropriate empirical antibiotic therapy at the national, regional, and institutional level.

Anti-Bacterial Agents↗

Clonal occurrences of multidrug-resistant Gram-negative bacilli: report from the Meropenem Yearly Susceptibility Test Information Collection Surveillance Program in the United States (2004).

The Meropenem Yearly Susceptibility Test Information Collection Program is a global, longitudinal resistance surveillance network of more than 100 medical centers worldwide monitoring the susceptibility of bacterial pathogens to carbapenems and other broad-spectrum agents. Between 1999 and 2004, a total of 10-16 US medical centers referred up to 200 nonduplicate isolates from clinical infections to a central processing laboratory. Over this 6-year period, the antimicrobial activity of 12 broad-spectrum agents was assessed against 15990 bacterial isolates using Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) reference methods. Analysis of the MIC results by year within organism species and/or organism groups revealed a continued decrease in fluoroquinolone susceptibility (ciprofloxacin and levofloxacin), especially among indole-positive Proteae (-22.1%), Escherichia coli (-17.0%), Enterobacter species (-10.0%), and Proteus mirabilis (-7.6%) isolates. Antibiogram analysis of strains demonstrating multidrug resistance from the same institutions were further characterized by automated ribotyping and pulsed-field gel electrophoresis to determine clonality. In 2004, a total of 165 selected multidrug-resistant (MDR) strains produced 64 different ribotypes with the largest representing 31 Escherichia coli isolates from 6 medical centers. Other clusters were also identified within single medical centers among Enterobacter cloacae (6 strains), Providencia stuartii (5 strains), and Morganella morganii (4 strains). A significant clonal outbreak encompassing 40 Acinetobacter baumannii isolates from 3 centers in a single endemic region was identified in 1999 and has persisted through 2004. Continued surveillance of these broad-spectrum antimicrobial agents against MDR pathogens appears warranted to monitor the incidence and spread of resistant clones causing serious infections. Possible emergence of resistance mechanisms via clonal dissemination proves to be among the principle threats that compromise carbapenem therapy, where meropenem maintains the broadest spectrum of coverage.

Anti-Bacterial Agents↗